1. Field of the Invention
The present invention relates to a dielectric waveguide, particularly a dielectric waveguide for use in a transmission line or an integrated circuit for the millimeter-wave band.
2. Description of the Related Art
Recently, the importance of the millimeter-wave band has increased. To achieve improvement in millimeter-wave techniques, the integrated-circuit technique is indispensable.
Various kinds of dielectric waveguides have been proposed to reduce the transmission loss of the high frequency signal in an integrated circuit. For example, a normal type dielectric line has a dielectric strip provided between two parallel electrically-conductive plates. Similarly, a grooved type dielectric waveguide has a dielectric strip provided between two electrically-conductive plates. A dielectric strip is inserted in grooves provided in the surfaces of the electrically-conductive plates. A winged type dielectric waveguide has an a pair of opposing dielectric plates, a dielectric line provided between the dielectric plates, and electrode plates deposited on the outer surfaces of the dielectric plates.
The inventors of the present invention have proposed a further new type of dielectric waveguide. The dielectric waveguide is disclosed in a laid open Japanese Patent Application No. Tokkai-Hei-9-23109. The dielectric waveguide has a dielectric strip and a circuit board both provided between two electrically-conductive plates. The circuit board may be in the vicinity of the dielectric strip to achieve electromagnetic-field coupling between a circuit element on the circuit board and the dielectric strip. Alternatively, a part of the circuit board may be inserted into the dielectric strip to achieve electromagnetic-field coupling between a circuit element on the circuit board and the dielectric strip.
However, to adjust the electromagnetic-field coupling between the circuit element and the dielectric strip, or the electromagnetic-field coupling between the dielectric strip and a strip line on the circuit board, it is necessary to locate the circuit board carefully. The same difficulty exists when locating a dielectric resonator which is to electromagnetically couple with a normal type, grooved type or winged type dielectric waveguide.